(1) Field of the Invention
The present invention relates to a unique cDNA derived from a disease resistant hybrid Elm Tree which encodes a chitinase, a signal peptide and a sorting peptide. In particular the present invention relates to cDNA as set forth in SEQ ID NO:1.
(2) Description of Related Art
Chitinases are pathogenesis response-related proteins found in a wide variety of plants. Several lines of evidence suggest strongly that chitinases are antifungal proteins. Accumulation of chitinase (Meins, F., Ahl, P., Plant Cell 61:155-161 (1989); Metraux, J. P., et al., Physiol Mol Plant Path 28:161-169 (1986); and Rasmussen, U., et al., Planta 187:328-334 (1992)) and mRNA encoding chitinase (Roby, D., et al., Plant Sci 52:175-185 (1987); Roby, D., et al., Physiological and Molecular Plant Pathology 33:409-417 (1988); and Meins, F., et al., Plant Cell 1:447-457 (1989)) are induced strongly during the course of a fungal infection. This induction is also seen when plant tissue is treated with fungal cell wall material (Kurosaki, F., et al., Physiol Mol Plant Path 31:211-216 (1987); Roby, D., et al., Biochem Biophys Res Comm 143(3):885-892 (1987)). Ethylene, a gaseous plant hormone also produced during the course of a fungal infection, strongly induces chitinase activity (Boller, T., Oxford Surveys of Plant Molecular and Cell Biology 5:145-174 (1988); and Boller, T., et al., Planta 157:22-31 (1983)). Finally, induction also results from wounding (Parsons, T. J., et al., Proc Natl Acad Sci USA 86:7895-7899 (1989)), conditions which could mimic cell death during an active infection.
WO 90/07001 to Broglie et al describes DNA encoding chitinases for use in inhibiting fungi in detail. The techniques described in this patent application are applicable to the present invention.
In elms, pathogenesis of the fungus Ophiostoma ulmi, the causative agent of Dutch elm disease (DED) is well understood as is the physiological response of the elm to infection. Very little, however, is known about the molecular mechanisms of elms' disease response, and nothing of the production of pathogenesis-related (PR) proteins, such as chitinase. Little is also known about what enables some species of elm to resist O. ulmi infection.